Water, blood or blood products, but also other body fluids or injection solutions, are purified by filtering these products. If it is desired at the same time as the purification also to achieve killing of pathogenic organisms, it is necessary to combine the filtration and purification step with measures which also bring about corresponding inactivation or killing of pathogenic organisms. Various processes and apparatus have been disclosed for this purpose. Thus, WO-92/040 31 discloses that blood, blood derivatives and other body fluids can be purified with soluble PVP-iodine products (povidone-iodine) by killing pathgenic organisms without this harming the substances to be purified. For this purpose, the liquid to be purified is treated with the povidone-iodine, and the liquid treated in this way is then passed through filters. The killed organisms and other impurities then remain in the filter cake, while the liquid which drains off contains the purified products. Although such a process is perfectly effective, it is a multistage process in which first the dissolved povidone-iodine is brought into contact with the liquid to be purified and subsequently filtration is then carried out. The distinct advantage of this process is that the dissolved povidone remains dissolved in the filtrate in this case (even after removal of the iodine) and is virtually impossible to remove again therefrom. The consequence of this is that a product of such a process can no longer be administered directly because it still contains the povidone which does not pass the kidneys.
DE-41 19 288 furthermore discloses the purification of pharmaceutical or biological and other liquids by layer filtration. Since such liquids are intended to be free of foreign constituents, especially metal ions, after the purification step, the only substances which can be used for such filters are those with which contamination of the filtrate by metals is not to be expected. This is why DE-41 19 288 proposes the use of filtration aids which have a low metal ion content and are preferably free of metal ions, such as fine highly dispersive polymer granules, micronized celluloses or mixtures of these substances as filtration-active component. Kieselguhr or perlite, which might be effective filtration aids, are unsuitable because of the metal content.
Wo 93/06911 describes a process for the filtration of blood using crospovidone-iodine in powder form. This is applied in the form of a bed to a filter. The process requires a crospovidone-iodine with a substantially uniform particle size of 40-150 .mu.m. This is industrially elaborate to produce. In addition, the killed microorganisms remain in the filtrate and must be removed therefrom. The separation of the cellular components of the blood, which have been filtered off, from the crospovidone-iodine is also elaborate and is difficult to implement on the industrial scale because of the narrow particle size distribution for the particle sizes required for use.
WO 94/00161 describes the treatment of blood or biological tissue with povidone-H.sub.2 O.sub.2 complexes as biocidal substances, it being possible to use both povidone and crospovidone as basis for the complexes. The biological materials can be treated in an apparatus in which layers of various biocidal substances are arranged one above the other.